As a conventional technique, there is a known flow data generating method performed using: a first storage part in which a group of two-item relationship data is stored where each record thereof has first item data, second item data, and data indicating type of two-item relationship between the first item data and the second item data; and a second storage part in which a position in the first storage part of each value stored as the first item data or the second item data is stored as positional data; the method including the steps of: extracting, from the group of the two-item relationship data in the first storage part, first two-item relationship data in which first item data is taken as data that is a starting point of flow data; associating the starting point as a parent node and the second item data of the first two-item relationship data as a child node; adding the two-item relationship type of the first two-item relationship data to an arc between the nodes; searching for third two-item relationship data having second item data of second two-item relationship data as first item data, from the group of the two-item relationship data in the first storage part, referring to the positional data in the second storage part; associating the first item of the thus extracted third two-item relationship data as a parent node and the second item data of the third two-item relationship data as a child node; and adding the two-item relationship type of the extracted two-item relationship data to an arc between the nodes; wherein this process is repeated to generate a subtree in which the second item data of the first two-item relationship data is taken as a root. See, for example, JP 2004-246879A at page 1 and FIG. 1.
However, such a conventional technique is problematic in that multiple nodes cannot be properly and easily arranged.
For example, according to such a conventional technique, if the number of nodes increases or the connection relationship between the nodes becomes complicated, the connected nodes are arranged to be distributed in a wide range, or the lines connecting the nodes and the like cross each other, resulting in a problem that the connection relationship between the nodes is not easily viewable. Furthermore, if a parent node cannot be specified, there is a problem that the node may not be properly arranged.